The invention can be used in particular to improve the sliding qualities of a window support carriage on a rail of a vehicle door "cassette" such as the one described in the French patent application filed by the applicant on Jan. 24, 1997 with registration number 97 00790.
The slide rails of the window support carriages for vehicle door cassettes can expand under the effect of thermal fluctuations. The deformation of the rails is hindered by the rail attachment screws in the shell of the door of the vehicle, these attachment screws generally being located at both ends of the rails. Thus, as it deforms, the rail can over its length acquire irregularities, in particular in locations hindered by the screws. Consequently, the rail can lose its regular curvature which can cause malfunction in the window crank mechanism; in particular, the window support carriages can become blocked. Moreover, the rail has to be made of a plastic material with good properties of mechanical resistance to stress and strain, good resistance to wear from the sliding of the runners and a good friction coefficient between the material comprising the rail and that comprising the runner. All the above requires the user to mold his rail with a very specific plastic material which is difficult to work with.